Analytical and Bioanalytical Chemistry

, Volume 410, Issue 9, pp 2377–2384 | Cite as

Determination of oligomers in virgin and recycled polyethylene terephthalate (PET) samples by UPLC-MS-QTOF

  • Sara Ubeda
  • Margarita Aznar
  • Cristina Nerín
Research Paper


An oligomer is a molecule that consists of a few monomer units. It can be formed during polymer manufacturing and also due to polymer degradation processes or even during use conditions. Since oligomers are not included in chemical databases, their identification is a complex process. In this work, the oligomers present in 20 different PET pellet samples have been determined. Two different sample treatment procedures, solvent extraction and total dissolution, were applied in order to select the most efficient one. The analyses were carried out by UPLC-MS-QTOF. The use of high resolution mass spectrometry allowed the structural elucidation of these compounds and their correct identification. The main oligomers identified were cyclic as well as lineal from the first, second, and third series. All of them were composed of terephthalic acid (TPA), diethylene glycol (DEG), and ethylene glycol (EG). Quantitative values were very different in both procedures. In total dissolution of PET samples, the concentration of oligomers was always, at least, 10 times higher than in solvent extraction; some of the compounds were only detected when total dissolution was used. Results showed that the oligomers with the highest concentration values were dimers and trimers, cyclic, as well as lineal, from the first and second series. The oligomer with the maximum concentration value was TPA2-EG-DEG that was found in all the samples in a concentration range from 2493 to 19,290 ng/g PET. No differences between virgin and recycled PET were found. Migration experiments were performed in two PET bottles, and results showed the transference of most of these oligomers to a fat food simulant (ethanol 95%).

Graphical abstract

Graphical abstract of the two procedures developd and optimized for identifying oligomers in PET pellets and in migration form PET bottles


Non-intentionally added substances (NIAS) Total dissolution Oligomers Polyethylene terephthalate (PET) Food contact material UPLC-MS-QTOF 


Compliance with ethical standards

Conflict of interest

The authors declare that they do not have potential conflicts of interest. No human participants or animals are involved in the research.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Analytical Chemistry, EINAUniversity of ZaragozaZaragozaSpain

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